Invalid variance: The type parameter 'T' must be contravariantly valid on 'UserQuery.IItem.ItemList'. 'T' is covariant [duplicate]

Answer 1

The setter is not allowed, since if it were you would be able to do this:

public interface ISubFoo : IFoo { }

IItem item = //whatever
item.ItemList = new List>>();

which is not type safe.